In a prior application of A. J. Josefson and L. R. Munson, Ser. No. 840,033, filed Oct. 6, 1977, it is found that certain anodic electrocoating systems are superior for the coating of aluminum, but without appropriate chromate pretreatment, the clear coated aluminum, while more corrosion resistant than usual, is still badly corroded. Using a typical Cr.sup.+3 chromate pretreatment provided by the product Alodine 401-45, the clear coated aluminum product provided in Ser. No. 840,033 is improved to a fair rating.
In contrast, and using preferred practice in this invention without chromate pretreatment, the corrosion resistance is very good. If the Alodine 401-45 chromate pretreatment of the aluminum substrate is also used, the corrosion resistance is still further improved to an excellent rating.